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P a g e |1 Name______________________________ Line & Bar Graphs Line graphs show relationships between two variables or sets of data. In other words, they show how one thing (variable) is affected by another variable and how the variables change depending on one another. Line graphs are useful for showing trends in data and for making predictions. They are very useful for showing trends over time; this means that they show how one variable is affected by the other as the variable increases or decreases. To make a quality line graph: 1. Put the independent (manipulated) variable on the X-axis. The X-axis is the horizontal axis on the bottom of the graph. 2. Put the dependent (responding) variable on the Y-axis. The Y-axis is the vertical axis on the side of the graph. 3. Decide on an appropriate scale for each axis. The scale is the numbers used on the axes of the graph. The scale usually begins at zero. The scale of the graph is very important. The same data can be plotted on different scales and not look like the same data at all. 4. Select an appropriate interval for your graph. The interval is the amount of space between one number and the next or one type of data and the next on the graph. The interval is just as important as the scale. 5. Label each axis. 6. Plot the data points. 7. Connect the data points with a line. 8. Give the graph a descriptive title that includes both variables. For example, Distance vs. Time, Plant Height vs. Fertilizer Amount, etc. One way to remember which data goes on which axis is DRY MIX D- Dependent M- Manipulated R- Responding I- Independent Y- Y-axis X- X-axis M. V. Poarch 2018 science-class.net Permission to copy granted for non-profit, educational use only. P a g e |2 Bar graphs are used to show data that are not continuous. A bar graph allows us to compare data like amounts or frequency or categories. They allow us to make generalizations and help see differences in data. Bar graphs also let us find the value of one variable when we know the value of the other. To make a quality bar graph: 1. Put the independent (amounts, frequencies, categories) variable on the X-axis. The X-axis is the horizontal axis on the bottom of the graph. 2. Put the dependent (what was measured) variable on the Y-axis. The Yaxis is the vertical axis on the side of the graph. 3. Decide on an appropriate scale for each axis. The scale is the numbers used on the axes of the graph. The scale usually begins at zero. Bar graphs frequently do not have numerical scales on the X-axis. The scale of the graph is very important. The same data can be plotted on different scales and not look like the same data at all. 4. Select an appropriate interval for your graph. The interval is the amount of space between one number and the next or one type of data and the next on the graph. The interval is just as important as the scale. 5. Label each axis. 6. For each of the specific independent variables (category, frequency, or amount) draw a solid bar to height of appropriate dependent variable. 7. Give the graph a descriptive title that includes both variables Remember, use a DRY MIX! D- Dependent M- Manipulated R- Responding I- Independent Y- Y-axis X- X-axis M. V. Poarch 2018 science-class.net Permission to copy granted for non-profit, educational use only. P a g e |3 Practice making a quality line graph using the San Antonio Spurs wins by season in the table below. Then make a quality bar graph containing wins and losses. Season Wins Losses 1997 20 62 1998 56 26 1999 37 13 2000 53 29 2001 58 24 2002 58 24 2003 60 22 2004 57 25 2005 59 23 2006 63 19 2007 58 24 2008 56 26 2009 54 28 2010 50 32 2011 61 21 2012 50 32 2013 58 24 2014 62 20 2015 55 27 2016 67 15 2017 61 21 M. V. Poarch 2018 science-class.net Permission to copy granted for non-profit, educational use only. P a g e |4 M. V. Poarch 2018 science-class.net Permission to copy granted for non-profit, educational use only. P a g e |5 M. V. Poarch 2018 science-class.net Permission to copy granted for non-profit, educational use only.